Offshore wind turbine environment, loads, simulation, and design

Vorpahl, Fabian; Schwarze, Holger; Fischer, Tim; Seidel, Marc; Jonkman, Jason

doi:10.1002/wene.52

Cited by 67 publications

(59 citation statements)

References 34 publications

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“…Wind turbines in an offshore environment are exposed to combined wind and wave loading, both of which are natural phenomena occurring in a stochastic, irregular manner. 2 The stochastic fluctuations of the wind are considered to be one of the most serious load problems for wind turbines and contribute considerably to material fatigue. 3 In numerical simulations, wind and wave loading are difficult to reproduce accurately, and this is therefore a significant cause of simulation error.…”

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confidence: 99%

The simulation error caused by input loading variability in offshore wind turbine structural analysis

Zwick

Muskulus

2014

Wind Energy

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Stochastic representations of turbulent wind and irregular waves are used in time domain simulations of offshore wind turbines. The variability due to finite sampling of this input loading is an important source of simulation error. For the OC4 reference jacket structure with a 5 MW wind turbine, an error of 12–34% for ultimate loads and 6–12% for fatigue loads can occur with a probability of 1%, for simulations with a total simulation length of 60 min and various load cases. In terms of fatigue life, in the worst case, the lifetime of a joint was thereby overestimated by 29%. The size of this error can be critical, i.e., ultimate or fatigue limits can be exceeded, with probability depending on the choice of number of random seeds and simulation length. The analysis is based on a large simulation study with about 30,000 time domain simulations. Probability density functions of response variables are estimated and analyzed in terms of confidence intervals; i.e., how probable it is to obtain results significantly different from the expected value when using a finite number of simulations. This simulation error can be reduced to the same extent, either using several short simulations with different stochastic representations of the wind field or one long simulation with corresponding total length of the wind field. When using several short‐term simulations, it is important that ultimate and fatigue loads are calculated based on the complete, properly combined set of results, in order to prevent a systematic bias in the estimated loads. Copyright © 2014 John Wiley & Sons, Ltd.

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confidence: 99%

The simulation error caused by input loading variability in offshore wind turbine structural analysis

Zwick

Muskulus

2014

Wind Energy

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“…The main use of such a model would be as a starting point for a probabilistic analysis. One of the main challenges for structural optimization of wind turbine support structures is the sheer amount of time-domain simulations needed for a comprehensive assessment, which borders on the region of a few thousands [2,5]. It would be highly welcome to obtain a more efficient, yet still highly accurate, way of predicting fatigue damage in a support structure.…”

Section: Discussionmentioning

confidence: 99%

Simplified rotor load models and fatigue damage estimates for offshore wind turbines

Muskulus

2015

Phil. Trans. R. Soc. A.

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The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in statespace form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations.

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“…Wind turbines are highly dynamic and tightly coupled systems that characterize a multiphysics problem, and their structural design and assessment pose specific challenges [24,25]. The rotor of a wind turbine is subject to aeroelastic effects that result in feedback of the rotor motion on the forces acting on the supporting structure.…”

Section: Aeroelastic Model and Decoupled Approachmentioning

confidence: 99%

Some Results on the Vulnerability Assessment of HAWTs Subjected to Wind and Seismic Actions

et al. 2017

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Abstract:The spread of the wind energy industry has caused the construction of wind farms in areas prone to high seismic activity. Accordingly, the analysis of wind turbine loading associated with earthquakes is of crucial importance for an accurate assessment of their structural safety. Within this topic, this paper presents some preliminary results of a probabilistic framework intended to be used for the estimation of the probability of failure of Horizontal Axis Wind Turbine-supporting structures when subjected to the wind and seismic actions. In particular, the multi-hazard fragility curves of the wind turbine-supporting structure were calculated using Monte Carlo simulations. A decoupling approach consisting of aerodynamic analysis of the rigid rotor blade model and subsequent linear dynamic Finite Element analyses of the supporting structure, including aerodynamic damping, was used. The failure condition of the tower structure was estimated according to the stress design procedure proposed by EC3 for the buckling limit state assessment. Finally, the vulnerability assessment of HAWTs to wind and seismic actions was evaluated in terms of fragility curves describing the probability of failure of the supporting tower structure as a function of the Peak Ground Acceleration (PGA) for each parked and operational wind condition. In particular, the results highlight a probability of failure larger than 50% for high levels of seismic action (PGA greater than 0.7 g) combined with the rotor in parked condition (wind speed of 3 m/s) or in operational rated condition (wind speed of 11.4 m/s).

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Offshore wind turbine environment, loads, simulation, and design

Cited by 67 publications

References 34 publications

The simulation error caused by input loading variability in offshore wind turbine structural analysis

The simulation error caused by input loading variability in offshore wind turbine structural analysis

Simplified rotor load models and fatigue damage estimates for offshore wind turbines

Some Results on the Vulnerability Assessment of HAWTs Subjected to Wind and Seismic Actions

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